laboratory applications because of their
limited reliability and lifetime, and their
need for cryogenic cooling. However,
in 2015, engineers at Coherent (Santa
Clara, CA) solved issues of CO laser reliability and developed a family of sealed
CO lasers that operate at room temperature, with lifetimes in the thousands-of-hours range.

The CO laser emits a cascade ofwavelengths around 5. 5 µm, whichis about half the primary wavelengthof the CO2 laser (at 10. 6 µm). Manymaterials, including glass, water, andmammalian tissues, have very dif-ferent absorption characteristics atthese shorter wavelengths. Applica-tions scientists at Art Photonics (Berlin,Germany) have recently been investi-gating how this difference in absorp-tion manifests in laser-tissue interac-tions using one of the new Coherentlasers. This is a first step towards inves-tigating the potential of these CO lasersas differentiated tools for surgical andrelated medical applications.

Many laser-surgery and other medical
applications require fiber delivery. As
explained by Viacheslav Artyushenko,
president of Art Photonics, the company
provides fiber light-delivery configurations from the ultraviolet through
infrared, including the difficult 4–16
µm region, within which flexible cables
are used that are based on polycrystalline infrared fibers (PIRs) extruded from
silver halide crystals.

“Preliminary work in the past with
an experimental CO laser indicated
that its shorter wavelength could be an
advantage in some surgical applications,
because in some instances the shorter
wavelength may provide up to two to
three times deeper penetration than
the CO2 laser,” Artyushenko says. “We
wanted to explore this further.”

Porcine tissue samples from fatty muscle
(left) and heart muscle (right) cut with light
from CO (top) and CO2 (bottom) lasers
operating at an 8 W output at a speed
of 4 mm/s are compared, with the beam
focused 2 mm below tissue surface in all
cases; the white zone shows the extent
of coagulation. These cross-sectional
microscope images were taken after
perpendicular cuts with a scalpel. (Courtesy
of Art Photonics)